Luminescent solar collector

ABSTRACT

Disclosed are fluorescent dye compounds of Formula (I) or (II): 
                         
where R, R′, m and k are as described herein. The dye compounds are suitable for use in luminescent solar collectors. Methods of making the dye compounds and luminescent solar collectors comprising them are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to Ser. No. 12/194,008 entitled “LUMINESCENTSOLAR COLLECTOR” and filed on Aug. 19, 2008; Ser. No. 12/194,097entitled “LUMINESCENT SOLAR COLLECTOR” and filed on Aug. 19, 2008; andSer. No. 12/194,199 entitled “LUMINESCENT SOLAR COLLECTOR” and filed onAug. 19, 2008. These three related applications are hereby incorporatedby reference in their entirety.

BACKGROUND

The present disclosure generally relates to luminescent solarcollectors. In particular, it relates to methods of increasing theconcentration of light at the edge of such a solar collector.

Luminescent solar collectors (LSCs), or luminescent solar concentrators,are beneficial for capturing solar energy for use. An LSC usuallycomprises a sheet, generally a molded polymer, having a surface area.Dispersed, dissolved, or doped within the sheet is a fluorescent dye.When the sheet is exposed to light (radiation energy), the dye absorbs aportion of the light and emits the absorbed light energy at different,longer wavelengths. This light is then transported, via total internalreflection, to at least one edge of the sheet. The concentration oflight from a large surface area to a smaller surface area (the edge) isalso known as the “edge glow” effect. Due to this effect, the amount oflight (i.e. energy) available at the edge is related to the totalsurface area of the sheet. A light energy converter, such as a siliconphotocell, can be attached to at least one edge of the LSC to convertthe light energy transmitted thereto into electricity. This enables theLSC to concentrate the maximum amount of light at its edge or edges togenerate more electrical power.

The amount of light (i.e. energy) available at the edge is related tothe total amount of incident light contacting the sheet; the type ofpolymer matrix; and the absorption and emission efficiencies (i.e.quantum yield) of the fluorescent dye. In summary, the edge emission isrelated to the total amount of light contacting the sheet which isabsorbed by a dye and eventually directed to the edge. Current LSCsystems harvest only a limited portion of the light which contacts thesheet because long wavelengths of 600 nanometers and greater are notabsorbed and/or the fluorescent dye has a low quantum yield (i.e. below80%). A high quantum yield is desirable because light lost duringfluorescence is also lost to the light energy converter. It is alsodesirable to collect as much of the light energy on the sheet aspossible to produce more unit power per area on the LSC.

BRIEF DESCRIPTION

Disclosed, in various embodiments, are fluorescent dyes suitable for usein luminescent solar collectors, methods for making such dye compounds,and luminescent solar collectors comprising such compounds. Theseluminescent solar collectors harvest portions of the visible lightspectrum which are otherwise lost.

Disclosed are fluorescent dyes of Formula (I) or (II):

wherein each R and R′ is independently selected from C₈-C₁₈ alkyl,substituted C₈-C₁₈ alkyl, C₈-C₁₈ alkoxy, substituted C₈-C₁₈ alkoxy, andhalogen; m represents the number of R substitutents on each phenoxyring, wherein each m is independently an integer from 0 to 5; and krepresents the number of R′ substitutents on each benzimidazole group,wherein each k is independently an integer from 0 to 4.

In specific embodiments, each phenoxy ring is substituted in only thepara position with an R group independently selected from C₈-C₁₈ alkyl.The four R groups in the para position may be the same.

The fluorescent dye may have a quantum yield of about 80% or greater,including 90% or greater and 95% or greater.

The fluorescent dye may have a maximum absorption wavelength of fromabout 600 nm to 650 nm and a maximum emission wavelength of 650 nm orgreater.

Specific fluorescent dyes of Formula (I) or (II) include those ofFormulas (III) through (VI) as described further below.

In other embodiments, a solar collector is disclosed which comprises asheet and a light energy converter operatively connected to the sheet;

-   -   the sheet comprising a thermoplastic polymer and a fluorescent        dye of Formula (I) or (II) dispersed therein, wherein each R and        R′ is independently selected from C₁-C₁₈ alkyl, substituted        C₁-C₁₈ alkyl, C₁-C₁₈ alkoxy, substituted C₁-C₁₈ alkoxy, and        halogen; each m is independently an integer from 0 to 5; and        each k is independently an integer from 0 to 4; and    -   wherein the fluorescent dye absorbs light and radiates the        absorbed light at a longer wavelength, and the sheet is        configured to transmit the radiated light to the light energy        converter; wherein the sheet has an edge emission output of        about 150 W/m² or greater when measured using a sheet of        dimensions 60 mm×60 mm×3.2 mm and exposed to a radiation        intensity of about 1000 W/m².

The fluorescent dye may be present in an amount of from about 0.001 toabout 1.0 weight percent, based on the total weight of the sheet. Thethermoplastic polymer may be a polycarbonate polymer or polymethylmethacrylate. The fluorescent dye may be that of Formula (III), (IV),(V), (VI), (VII), or (VIII), as described further below.

A method of forming a fluorescent dye of Formula (I) or (II) is alsodisclosed, the method comprising:

-   -   condensing a tetrachloroperylene dianhydride with an o-phenylene        diamine to form an intermediate; and    -   reacting the intermediate with a base and a phenol of Formula        (IX), as described further below, in an aprotic polar solvent to        form the fluorescent dye of Formula (I) or (II).

The condensing step may be performed at a temperature of from about 80°C. to about 200° C. The condensing step may be performed over a timeperiod of from about 3 hours to about 12 hours. The condensing step maybe performed in an organic solvent, such as propionic acid, acetic acid,imidazole, quinoline, isoquinoline, N-methylpyrrolidone,dimethylformamide, and halogenated solvents.

The reacting step may be performed at a temperature of from about 80° C.to about 200° C. The reacting step may be performed over a time periodof from about 4 hours to about 36 hours. The base may comprise sodium orpotassium. The aprotic polar solvent may be dimethylformamide,n-methylpyrrolidone, dimethyl sulfoxide, or dimethylacetamide.

These and other non-limiting characteristics of the luminescent solarcollectors of the present disclosure are more particularly describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is a diagram of a process for synthesizing dye compounds of thepresent disclosure.

FIG. 2 is an elevated view of a luminescent solar collector.

FIG. 3 is a side view of a first exemplary embodiment of the luminescentsolar collector.

DETAILED DESCRIPTION

A more complete understanding of the components, processes andapparatuses disclosed herein can be obtained by reference to theaccompanying drawings. These drawings are merely schematicrepresentations based on convenience and the ease of demonstrating thepresent disclosure, and are, therefore, not intended to indicaterelative size and dimensions of the devices or components thereof and/orto define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

Numerical values in the specification and claims of this application,particularly as they relate to polymer compositions, reflect averagevalues for a composition that may contain individual polymers ofdifferent characteristics. Furthermore, unless indicated to thecontrary, the numerical values should be understood to include numericalvalues which are the same when reduced to the same number of significantfigures and numerical values which differ from the stated value by lessthan the experimental error of conventional measurement technique of thetype described in the present application to determine the value.

The present disclosure may be understood more readily by reference tothe following detailed description of desired embodiments and theexamples included therein. In the following specification and the claimswhich follow, reference will be made to a number of terms which shall bedefined to have the following meanings.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. All ranges disclosed herein areinclusive of the recited endpoint and independently combinable (forexample, the range of “from 2 grams to 10 grams” is inclusive of theendpoints, 2 grams and 10 grams, and all the intermediate values).

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (forexample, it includes at least the degree of error associated with themeasurement of the particular quantity).

The term “integer” means a whole number and includes zero. For example,the expression “n is an integer from 0 to 4” means n may be any wholenumber from 0 to 4, including 0.

Compounds are described using standard nomenclature. For example, anyposition not substituted by any indicated group is understood to haveits valency filled by a bond as indicated, or a hydrogen atom. A dash(“—”) that is not between two letters or symbols is used to indicate apoint of attachment for a substituent. For example, the aldehyde group—CHO is attached through the carbon of the carbonyl group.

The term “aliphatic” refers to a linear or branched array of atoms thatis not cyclic and has a valence of at least one. Aliphatic groups aredefined to comprise at least one carbon atom. The array of atoms mayinclude heteroatoms such as nitrogen, sulfur, silicon, selenium andoxygen or may be composed exclusively of carbon and hydrogen (“Alkyl”).Aliphatic groups may be substituted or unsubstituted. Exemplaryaliphatic groups include, but are not limited to, methyl, ethyl,isopropyl, isobutyl, chloromethyl, hydroxymethyl (—CH₂OH),mercaptomethyl (—CH₂SH), methoxy, methoxycarbonyl (CH₃OCO—), nitromethyl(—CH₂NO₂), and thiocarbonyl.

The term “alkyl” refers to a linear or branched array of atoms that iscomposed exclusively of carbon and hydrogen. The array of atoms mayinclude single bonds, double bonds, or triple bonds (typically referredto as alkane, alkene, or alkyne). Alkyl groups may be substituted orunsubstituted. Exemplary alkyl groups include, but are not limited to,methyl, ethyl, and isopropyl.

The term “aromatic” refers to an array of atoms having a valence of atleast one and comprising at least one aromatic group. The array of atomsmay include heteroatoms such as nitrogen, sulfur, selenium, silicon andoxygen, or may be composed exclusively of carbon and hydrogen. Thearomatic group may also include nonaromatic components. For example, abenzyl group is an aromatic group that comprises a phenyl ring (thearomatic component) and a methylene group (the nonaromatic component).Exemplary aromatic groups include, but are not limited to, phenyl,pyridyl, furanyl, thienyl, naphthyl, biphenyl, 4-trifluoromethylphenyl,4-chloromethylphen-1-yl, and 3-trichloromethylphen-1-yl(3-CCl₃Ph-).

The terms “cycloaliphatic” and “cycloalkyl” refer to an array of atomswhich is cyclic but which is not aromatic. The cycloaliphatic group mayinclude heteroatoms such as nitrogen, sulfur, selenium, silicon andoxygen, or may be composed exclusively of carbon and hydrogen. Acycloalkyl group is composed exclusively of carbon and hydrogen. Acycloaliphatic group may comprise one or more noncyclic components. Forexample, a cyclohexylmethyl group (C₆H₁₁CH₂) is a cycloaliphaticfunctionality, which comprises a cyclohexyl ring (the array of atomswhich is cyclic but which is not aromatic) and a methylene group (thenoncyclic component). Exemplary cycloaliphatic groups include, but arenot limited to, cyclopropyl, cyclobutyl, 1,1,4,4-tetramethylcyclobutyl,piperidinyl, and 2,2,6,6-tetramethylpiperydinyl.

The term “alkoxy” refers to an array of atoms containing an alkyl groupand an oxygen atom at one end. Alkyl groups may be substituted orunsubstituted. Exemplary alkoxy groups include methoxy(—OCH₃) andethoxy(—OCH₂CH₃). A related group is “phenoxy,” which refers to a phenylgroup having an oxygen atom attached to one carbon. The phenoxy groupmay also be substituted or unsubstituted.

The present application discloses a dye compound of Formula (I) or (II):

wherein each R and R′ is independently selected from C₁-C₁₈ alkyl,substituted C₁-C₁₈ alkyl, C₁-C₁₈ alkoxy, substituted C₁-C₁₈ alkoxy, andhalogen; m represents the number of R substitutents on each phenoxyring, wherein each m is independently an integer from 0 to 5; and krepresents the number of R′ substitutents on each benzimidazole group,wherein each k is independently an integer from 0 to 4. The compoundscan be considered as having a perylene core, two benzimidazole endgroups (trans and cis isomers), and four phenoxy side groups. Thehydrogen atoms of the alkyl and alkoxy groups may be substituted with,for example, hydroxyl and phenyl groups.

In some specific embodiments, each phenoxy group is substituted in onlythe para position with an R group independently selected from C₈-C₁₈alkyl (with respect to the oxygen atom) (i.e. m=1). In more specificembodiments, the four R groups in the para position are the same. Inother specific embodiments, each k is zero.

In particular embodiments, each R and R′ is independently selected fromC₈-C₁₈ alkyl, substituted C₈-C₁₈ alkyl, C₈-C₁₈ alkoxy, substitutedC₈-C₁₈ alkoxy, and halogen; each m is independently an integer from 0 to5; and each k is independently an integer from 0 to 4.

Exemplary compounds include those of Formulas (III) through (VIII):

The compounds of Formula (I) and (II) generally have a maximumabsorption wavelength of from about 600 nanometers to 650 nanometers,and a maximum emission wavelength of 650 nanometers or greater. They mayalso have a quantum yield of about 80% or greater, including 90% orgreater and 95% or greater.

An exemplary diagram showing the synthesis of the dye compounds ofFormula (I) and (II) is shown in FIG. 1. The dye compounds of Formulas(I) and (II) can be synthesized by condensing a tetrachloroperylenedianhydride 1 with an o-phenylene diamine 2 in an appropriate solvent 3.The intermediate product 4 formed from the reaction of thetetrachloroperylene dianhydride and o-phenylene diamine can be usedwithout purification or separation. The intermediate product is thenreacted with a base 5 and a phenol 6 in an aprotic polar solvent 7 toobtain the dye compound 8 of Formula (I) or (II) (here, only Formula (I)is shown).

The o-phenylene diamine (also known as diaminobenzene) is used to formthe benzimidazole end groups of the dye compound. If desired,substituted o-phenylene diamines may also be used. The o-phenylenediamines may be substituted with C₁-C₁₈ alkyl, substituted C₁-C₁₈ alkyl,C₁-C₁₈ alkoxy, substituted C₁-C₁₈ alkoxy, and halogen.

Appropriate solvents for the condensation of the tetrachloroperylenedianhydride and o-phenylene diamine include propionic acid, acetic acid,imidazole, quinoline, isoquinoline, N-methylpyrrolidone,dimethylformamide, and halogenated solvents like o-dichlorobenzene.

The phenol reacts with the base to form a phenol salt that more easilyreacts with the intermediate product. In specific embodiments, the baseis a potassium or sodium base. Exemplary bases include potassiumcarbonate (K₂CO₃), sodium carbonate, and similar bases. Especiallydesirable are bases having a pKa of 10 or less.

The phenol used to react with the intermediate product generally has thestructure of Formula (IX):

where R and m are as described above. Exemplary phenols include nonylphenol; p-tert-butyl phenol; and p-tert-octyl phenol.

Suitable aprotic polar solvents include dimethylformamide (DMF);n-methyl pyrrolidone (NMP); dimethyl sulfoxide (DMSO);dimethylacetamide; and halogenated solvents like o-dichlorobenzene.

The condensing reaction of the tetrachloroperylene dianhydride ando-phenylene diamine can be performed at temperatures of from about 80°C. to about 200° C. The condensing reaction may take place over a timeperiod of from about 3 hours to about 12 hours, including from about 4hours to about 8 hours.

The reaction of the intermediate product with the base and the phenolcan be performed at temperatures of from about 80° C. to about 200° C.In more specific embodiments, the temperature is from about 130° C. toabout 160° C. The condensing reaction may take place over a time periodof from about 4 hours to about 36 hours. In more specific embodiments,the time period is from about 4 hours to about 28 hours. The reaction ofthe intermediate product with the base and the phenol may also takeplace in an inert atmosphere, such as under nitrogen or argon gas.Desirably, the solvent is “dry”, i.e. contains as little water aspossible.

After the dye compound of Formula (I) or (II) is formed, it may bepurified by column chromatography. The dye compounds are soluble incommon solvents like chlorobenzene, dichlorobenzene, toluene,chloroform, and dichloromethane. The dye compound of Formula (I) or (II)is particularly useful as a fluorescent dye in a luminescent solarcollector (LSC).

Referring to FIGS. 2 and 3, a luminescent solar collector (LSC) 10comprises a sheet (or panel) 20. The sheet or panel has two opposingsurfaces 30, 40. The opposing surfaces 30, 40 are joined by at least oneedge 50. For the sheet depicted, there are three additional connectingedges 60, 70, 80. The sheet comprises a thermoplastic polymer andfluorescent dye molecules 100 dispersed evenly therein. A light energyconverter, such as a photocell 90, is mounted or operatively connectedto the at least one connecting edge 50 to convert the light toelectricity. For example, the operative connection may be made by meansincluding, but not limited to, glueing the converter to the edge,mounting it in a slit, or by positioning it along the edge. Edgeemission may be measured in watts per square meter (W/m²). It ismeasured where the operative connection to the light energy converter ismade. In this embodiment, the edge emission is measured is at theconnecting edge 50. The area in the denominator is that of the edge 50,not that of the surface 30.

As explained above, light 110 is absorbed by the fluorescent dyemolecules 100. The molecules 100 then emit light 120 with a Stokes shift(i.e. towards a higher wavelength). The emitted light, due to totalinternal reflection, is guided towards the edge 50 of the sheet wherethe photocell 90 is located. The other edges 60, 70, 80 may be coated,for example with a mirror coating to reflect light towards edge 50 aswell. An opposing surface 40 may also be coated to reflect light aswell.

The sheet 20 is wide in two dimensions and thinner in the thirddimension (its thickness). The opposing surfaces 30, 40 of the sheet 20are generally parallel to each other, but need not be. It is alsocontemplated that the sheet 20 may be molded into various shapes. Forexample, the sheet may have the shape of a pyramidal frustum, a box, oras the surface of a hemisphere. The sheet may also vary in thickness. Inparticular embodiments, the sheet is planar. This shape is contemplatedfor use, for example, on the side or rooftop of a building, such as ahouse.

The sheet of the LSC comprises a thermoplastic polymer and a fluorescentdye. Types of thermoplastic polymers that are useful comprisepolycarbonates, including homopolycarbonates, copolycarbonates,polyester-polycarbonates, and polysiloxane-polycarbonates; polyestersincluding poly(alkylene terephthalate); polyetherimides;polysiloxane-polyetherimides; polyphenylene ethers; polyolefins;addition polymers, including homopolymers and copolymers, especiallyhomopolymers of alkenylaromatic compounds, such as polystyrenes, andcopolymers of alkenylaromatic compounds, such as impact modifiedpoly(alkenylaromatic) copolymers with ethylenically unsaturatednitrites, and poly(meth)acrylates, particularly polymethyl methacrylate.

In particular embodiments, the thermoplastic polymer is a polycarbonate.As used herein, the terms “polycarbonate” and “polycarbonate resin” meancompositions having repeating structural carbonate units of the formula(1):

in which at least 60 percent of the total number of R¹ groups arearomatic organic radicals and the balance thereof are aliphatic,alicyclic, or aromatic radicals. In one embodiment, each R¹ is anaromatic organic radical, for example a radical of the formula (2):-A¹-Y¹-A²-  (2)wherein each of A¹ and A² is a monocyclic divalent aryl radical and Y¹is a bridging radical having one or two atoms that separate A¹ from A².In an exemplary embodiment, one atom separates A¹ from A². Illustrativenon-limiting examples of radicals of this type are —O—, —S—, —S(O)—,—S(O)₂—, —C(O)—, methylene, cyclohexyl-methylene,2-[2.2.1]-bicycloheptylidene, ethylidene, isopropylidene,neopentylidene, cyclohexylidene, cyclopentadecylidene,cyclododecylidene, and adamantylidene. The bridging radical Y¹ may be ahydrocarbon group or a saturated hydrocarbon group such as methylene,cyclohexylidene, or isopropylidene.

Polycarbonates may be produced by the interfacial reaction of dihydroxycompounds having the formula HO—R¹—OH, which includes dihydroxycompounds of formula (3)HO-A¹-Y¹-A²-OH  (3)wherein Y¹, A¹ and A² are as described above. Also included arebisphenol compounds of general formula (4):

wherein R^(a) and R^(b) each represent a halogen atom or a monovalenthydrocarbon group and may be the same or different; p and q are eachindependently integers of 0 to 4; and X^(a) represents one of the groupsof formula (5):

wherein R^(c) and R^(d) each independently represent a hydrogen atom ora monovalent linear or cyclic hydrocarbon group and R^(e) is a divalenthydrocarbon group.

In an embodiment, a heteroatom-containing cyclic alkylidene groupcomprises at least one heteroatom with a valency of 2 or greater, and atleast two carbon atoms. Heteroatoms for use in the heteroatom-containingcyclic alkylidene group include —O—, —S—, and —N(Z)—, where Z is asubstituent group selected from hydrogen, hydroxy, C₁₋₁₂ alkyl, C₁₋₁₂alkoxy, or C₁₋₁₂ acyl. Where present, the cyclic alkylidene group orheteroatom-containing cyclic alkylidene group may have 3 to 20 atoms,and may be a single saturated or unsaturated ring, or fused polycyclicring system wherein the fused rings are saturated, unsaturated, oraromatic.

Other bisphenols containing substituted or unsubstituted cyclohexaneunits can be used, for example bisphenols of formula (6):

wherein each R^(f) is independently hydrogen, C₁₋₁₂ alkyl, or halogen;and each R^(g) is independently hydrogen or C₁₋₁₂ alkyl. Thesubstituents may be aliphatic or aromatic, straight chain, cyclic,bicyclic, branched, saturated, or unsaturated. Suchcyclohexane-containing bisphenols, for example the reaction product oftwo moles of a phenol with one mole of a hydrogenated isophorone, areuseful for making polycarbonate polymers with high glass transitiontemperatures and high heat distortion temperatures. Cyclohexyl bisphenolcontaining polycarbonates, or a combination comprising at least one ofthe foregoing with other bisphenol polycarbonates, are supplied by BayerCo. under the APEC® trade name.

Other useful dihydroxy compounds having the formula HO—R¹—OH includearomatic dihydroxy compounds of formula (7):

wherein each R^(h) is independently a halogen atom, a C₁₋₁₀ hydrocarbylsuch as a C₁₋₁₀ alkyl group, a halogen substituted C₁₋₁₀ hydrocarbylsuch as a halogen-substituted C₁₋₁₀ alkyl group, and n is 0 to 4. Thehalogen is usually bromine.

Specific examples of bisphenol compounds that may be represented byformula (3) include 1,1-bis(4-hydroxyphenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane(hereinafter “bisphenol-A” or “BPA”), 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)n-butane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxy-t-butylphenyl)propane,3,3-bis(4-hydroxyphenyl)phthalimidine,2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PPPBP), and1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (DMBPC). Combinationscomprising at least one of the foregoing dihydroxy compounds may also beused.

In a specific embodiment, the polycarbonate is a linear homopolymerderived from bisphenol-A, in which each of A¹ and A² is p-phenylene andY¹ is isopropylidene. The polycarbonates may have an intrinsicviscosity, as determined in chloroform at 25° C., of from about 0.3 toabout 1.5 deciliters per gram (dl/g), specifically from about 0.45 toabout 1.0 dl/g. The polycarbonates may have a weight average molecularweight (Mw) of from about 10,000 to about 100,000, as measured by gelpermeation chromatography (GPC) using a crosslinked styrene-divinylbenzene column, at a sample concentration of 1 milligram per milliliter,and as calibrated with polycarbonate standards.

In an embodiment, the polycarbonate has a melt volume flow rate (oftenabbreviated MVR). The MVR measures the rate at which a thermoplasticpasses vertically through a capillary under a defined weight load. TheMVR is measured in cubic cm per 10 minutes (cc/10 min). Polycarbonatesuseful for the formation of thin articles may have an MVR, measured at300° C. under a load of 1.2 kg according to ASTM D1238-04, of from about0.5 to about 80 cubic centimeters per 10 minutes (cc/10 min). In aspecific embodiment, a useful polycarbonate composition has an MVRmeasured at 300° C. under a load of 1.2 kg according to ASTM D1238-04,of from about 0.5 to about 50 cc/10 min, specifically from about 0.5 toabout 25 cc/10 min, and more specifically from about 1 to about 15 cc/10min. Mixtures of polycarbonates of different flow properties may be usedto achieve the overall desired flow property.

The polycarbonate may have a light transmittance greater than or equalto about 55%, specifically greater than or equal to about 60% and morespecifically greater than or equal to about 70%, as measured using amolded article of 3.2±0.12 millimeters thickness and consisting of thepolycarbonate, according to ASTM D1003-00. The polycarbonate may alsohave a haze less than or equal to about 5%, specifically less than orequal to about 4%, and most specifically less than or equal to about 3%,as measured using a molded article of 3.2±0.12 millimeters thickness andconsisting of the polycarbonate, according to ASTM D1003-00.

“Polycarbonates” and “polycarbonate resins” as used herein furtherinclude homopolycarbonates, copolymers comprising different R¹ moietiesin the carbonate (referred to herein as “copolycarbonates”), copolymerscomprising carbonate units and other types of polymer units, such asester units, polysiloxane units, and combinations comprising at leastone of homopolycarbonates and copolycarbonates. As used herein,“combination” is inclusive of blends, mixtures, alloys, reactionproducts, and the like. A specific type of copolymer is a polyestercarbonate, also known as a polyester-polycarbonate. Such copolymersfurther contain, in addition to recurring carbonate chain units of theformula (1), repeating units of formula (8):

wherein R² is a divalent group derived from a dihydroxy compound, andmay be, for example, a C₂₋₁₀ alkylene group, a C₆₋₂₀ alicyclic group, aC₆₋₂₀ aromatic group or a polyoxyalkylene group in which the alkylenegroups contain 2 to about 6 carbon atoms, specifically 2, 3, or 4 carbonatoms; and T divalent group derived from a dicarboxylic acid, and maybe, for example, a C₂₋₁₀ alkylene group, a C₆₋₂₀ alicyclic group, aC₆₋₂₀ alkyl aromatic group, or a C₆₋₂₀ aromatic group.

In an embodiment, R² is a C₂₋₃₀ alkylene group having a straight chain,branched chain, or cyclic (including polycyclic) structure. In anotherembodiment, R² is derived from an aromatic dihydroxy compound of formula(4) above. In another embodiment, R² is derived from an aromaticdihydroxy compound of formula (7) above.

Polycarbonates can be manufactured by processes such as interfacialpolymerization and melt polymerization. Although the reaction conditionsfor interfacial polymerization may vary, an exemplary process generallyinvolves dissolving or dispersing a dihydric phenol reactant in aqueouscaustic soda or potash, adding the resulting mixture to a suitablewater-immiscible solvent medium, and contacting the reactants with acarbonate precursor in the presence of a catalyst such as triethylamineor a phase transfer catalyst, under controlled pH conditions, e.g.,about 8 to about 10. The most commonly used water immiscible solventsinclude methylene chloride, 1,2-dichloroethane, chlorobenzene, toluene,and the like.

Carbonate precursors include, for example, a carbonyl halide such ascarbonyl bromide or carbonyl chloride, or a haloformate such as abishaloformates of a dihydric phenol (e.g., the bischloroformates ofbisphenol-A, hydroquinone, or the like) or a glycol (e.g., thebishaloformate of ethylene glycol, neopentyl glycol, polyethyleneglycol, or the like). Combinations comprising at least one of theforegoing types of carbonate precursors may also be used. In anexemplary embodiment, an interfacial polymerization reaction to formcarbonate linkages uses phosgene as a carbonate precursor, and isreferred to as a phosgenation reaction.

Among the phase transfer catalysts that may be used are catalysts of theformula (R³)₄Q⁺X, wherein each R³ is the same or different, and is aC₁₋₁₀ alkyl group; Q is a nitrogen or phosphorus atom; and X is ahalogen atom or a C₁₋₈ alkoxy group or C₆₋₁₈ aryloxy group. Useful phasetransfer catalysts include, for example, [CH₃(CH₂)₃]₄NX, [CH₃(CH₂)₃]₄PX,[CH₃(CH₂)₅]₄NX, [CH₃(CH₂)₆]₄NX, [CH₃(CH₂)₄]₄NX, CH₃[CH₃(CH₂)₃]₃NX, andCH₃[CH₃(CH₂)₂]₃NX, wherein X is Cl⁻, BR⁻, a C₁₋₈ alkoxy group or a C₆₋₁₈aryloxy group. An effective amount of a phase transfer catalyst may beabout 0.1 to about 10 wt % based on the weight of bisphenol in thephosgenation mixture. In another embodiment an effective amount of phasetransfer catalyst may be about 0.5 to about 2 wt % based on the weightof bisphenol in the phosgenation mixture.

Branched polycarbonate blocks may be prepared by adding a branchingagent during polymerization. These branching agents includepolyfunctional organic compounds containing at least three functionalgroups selected from hydroxyl, carboxyl, carboxylic anhydride,haloformyl, and mixtures of the foregoing functional groups. Specificexamples include trimellitic acid, trimellitic anhydride, trimellitictrichloride, tris-p-hydroxy phenyl ethane, isatin-bis-phenol,tris-phenol TC (1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene),tris-phenol PA (4(4(1,1-bis(p-hydroxyphenyl)-ethyl)alpha,alpha-dimethylbenzyl)phenol), 4-chloroformyl phthalic anhydride, trimesic acid, andbenzophenone tetracarboxylic acid. The branching agents may be added ata level of about 0.05 to about 2.0 wt %. Mixtures comprising linearpolycarbonates and branched polycarbonates may be used.

A chain stopper (also referred to as a capping agent) may be includedduring polymerization. The chain stopper controls molecular weight inthe polycarbonate. Exemplary chain stoppers include certainmono-phenolic compounds, mono-carboxylic acid chlorides, and/ormono-chloroformates.

Alternatively, melt processes may be used to make the polycarbonates.Generally, in the melt polymerization process, polycarbonates may beprepared by co-reacting, in a molten state, the dihydroxy reactant(s)and a diaryl carbonate ester, such as diphenyl carbonate, in thepresence of a transesterification catalyst in a Banbury° mixer, twinscrew extruder, or the like to form a uniform dispersion. Volatilemonohydric phenol is removed from the molten reactants by distillationand the polymer is isolated as a molten residue. A specifically usefulmelt process for making polycarbonates uses a diaryl carbonate esterhaving electron-withdrawing substituents on the aryls. Melt processesare generally carried out in a series of stirred tank reactors. Thereaction can be carried out by either a batch mode or a continuous mode.The apparatus in which the reaction is carried out can be any suitabletank, tube, or column. Continuous processes usually involve the use ofone or more continuous-stirred tank reactors (CSTRs) and one or morefinishing reactors.

Polyester-polycarbonates may also be prepared by interfacialpolymerization. Rather than utilizing the dicarboxylic acid per se, itis possible, and sometimes even preferred, to employ the reactivederivatives of the acid, such as the corresponding acid halides, inparticular the acid dichlorides and the acid dibromides. Thus, forexample instead of using isophthalic acid, terephthalic acid, or acombination comprising at least one of the foregoing, it is possible toemploy isophthaloyl dichloride, terephthaloyl dichloride, and acombination comprising at least one of the foregoing.

In addition to the polycarbonates described above, combinations of thepolycarbonate with other thermoplastic polymers, for examplecombinations of homopolycarbonates and/or polycarbonate copolymers withpolyesters, may be used. Useful polyesters may include, for example,polyesters having repeating units of formula (8), which includepoly(alkylene dicarboxylates), liquid crystalline polyesters, andpolyester copolymers. The polyesters described herein are generallycompletely miscible with the polycarbonates when blended.

Useful polyesters may include aromatic polyesters, poly(alkylene esters)including poly(alkylene arylates), and poly(cycloalkylene diesters).Aromatic polyesters may have a polyester structure according to formula(8), wherein D and T are each aromatic groups as described hereinabove.Also contemplated are aromatic polyesters with a minor amount, e.g.,about 0.5 to about 10 wt %, based on the total weight of the polyester,of units derived from an aliphatic diacid and/or an aliphatic polyol tomake copolyesters. Poly(alkylene arylates) may have a polyesterstructure according to formula (8), wherein T comprises groups derivedfrom aromatic dicarboxylates, cycloaliphatic dicarboxylic acids, orderivatives thereof. Specifically, where T is 1,4-phenylene, thepoly(alkylene arylate) is a poly(alkylene terephthalate). Examples ofpoly(alkylene terephthalates) include poly(ethylene terephthalate)(PET), poly(1,4-butylene terephthalate) (PBT), and poly(propyleneterephthalate) (PPT). Also useful are poly(alkylene naphthoates), suchas poly(ethylene naphthanoate) (PEN), and poly(butylene naphthanoate)(PBN). A useful poly(cycloalkylene diester) ispoly(cyclohexanedimethylene terephthalate) (PCT). Combinationscomprising at least one of the foregoing polyesters may also be used.

Copolymers comprising alkylene terephthalate repeating ester units withother ester groups may also be useful. Useful ester units may includedifferent alkylene terephthalate units, which can be present in thepolymer chain as individual units, or as blocks of poly(alkyleneterephthalates). Specific examples of such copolymers includepoly(cyclohexanedimethylene terephthalate)-co-poly(ethyleneterephthalate), abbreviated as PETG where the polymer comprises greaterthan or equal to 50 mol % of poly(ethylene terephthalate), andabbreviated as PCTG where the polymer comprises greater than 50 mol % ofpoly(1,4-cyclohexanedimethylene terephthalate).

Poly(cycloalkylene diester)s may also include poly(alkylenecyclohexanedicarboxylate)s. Of these, a specific example ispoly(1,4-cyclohexane-dimethanol-1,4-cyclohexanedicarboxylate) (PCCD),having recurring units of formula (9):

wherein, as described using formula (8), R² is a1,4-cyclohexanedimethylene group derived from 1,4-cyclohexanedimethanol,and T is a cyclohexane ring derived from cyclohexanedicarboxylate or achemical equivalent thereof, and may comprise the cis-isomer, thetrans-isomer, or a combination comprising at least one of the foregoingisomers.

The polyester-polycarbonates may have a weight-average molecular weight(M_(w)) of from about 1,500 to about 100,000, specifically from about1,700 to about 50,000, and more specifically from about 2,000 to about40,000. Molecular weight determinations are performed using gelpermeation chromatography (GPC), using a crosslinkedstyrene-divinylbenzene column and calibrated to polycarbonatereferences. Samples are prepared at a concentration of about 1 mg/ml,and are eluted at a flow rate of about 1.0 ml/min.

Where used, it is desirable for a polyester-polycarbonate to have an MVRof about 5 to about 150 cc/10 min., specifically about 7 to about 125cc/10 min, more specifically about 9 to about 110 cc/10 min, and stillmore specifically about 10 to about 100 cc/10 min., measured at 300° C.and a load of 1.2 kilograms according to ASTM D1238-04. Commercialpolyester blends with polycarbonate are marketed under the trade nameXYLEX®, including for example XYLEX® X7300, and commercialpolyester-polycarbonates are marketed under the tradename LEXAN® SLXpolymers, including for example LEXAN® SLX-9000, and are available fromSABIC Innovative Plastics.

The polycarbonate may also be a polysiloxane-polycarbonate copolymer,also referred to as a polysiloxane-polycarbonate. The polysiloxane (alsoreferred to herein as “polydiorganosiloxane”) blocks of the copolymercomprise repeating siloxane units (also referred to herein as“diorganosiloxane units”) of formula (10):

wherein each occurrence of R is same or different, and is a C₁₋₁₃monovalent organic radical. For example, R may independently be a C₁-C₁₃alkyl group, C₁-C₁₃ alkoxy group, C₂-C₁₃ alkenyl group, C₂-C₁₃alkenyloxy group, C₃-C₆ cycloalkyl group, C₃-C₆ cycloalkoxy group,C₆-C₁₄ aryl group, C₆-C₁₀ aryloxy group, C₇-C₁₃ arylalkyl group, C₇-C₁₃arylalkoxy group, C₇-C₁₃ alkylaryl group, or C₇-C₁₃ alkylaryloxy group.The foregoing groups may be fully or partially halogenated withfluorine, chlorine, bromine, or iodine, or a combination thereof.Combinations of the foregoing R groups may be used in the samecopolymer.

The value of D in formula (10) may vary widely depending on the type andrelative amount of each component in the polymer, the desired propertiesof the polymer, and like considerations. Generally, D may have anaverage value of 2 to 1,000, specifically 2 to 500, and morespecifically 5 to 100. Where D is of a lower value, e.g., less than 40,it may be desirable to use a relatively larger amount of thepolycarbonate-polysiloxane copolymer. Conversely, where D is of a highervalue, e.g., greater than 40, it may be necessary to use a relativelylower amount of the polycarbonate-polysiloxane copolymer.

In one embodiment, the polydiorganosiloxane blocks are provided byrepeating structural units of formula (11):

wherein D is as defined above; each R may independently be the same ordifferent, and is as defined above; and each Ar may independently be thesame or different, and is a substituted or unsubstituted C₆-C₃₀ aryleneradical, wherein the bonds are directly connected to an aromatic moiety.Useful Ar groups in formula (11) may be derived from a C₆-C₃₀dihydroxyarylene compound, for example a dihydroxyarylene compound offormula (3), (4), or (7) above. Combinations comprising at least one ofthe foregoing dihydroxyarylene compounds may also be used.

Units of formula (11) may be derived from the corresponding dihydroxycompound of formula (12):

wherein R, Ar, and D are as described above. Compounds of formula (12)may be obtained by the reaction of a dihydroxyarylene compound with, forexample, an alpha, omega-bisacetoxypolydiorganosiloxane under phasetransfer conditions.

In another embodiment, polydiorganosiloxane blocks comprise units offormula (13):

wherein R and D are as described above, and each occurrence of R⁴ isindependently a divalent C₁-C₃₀ alkylene, and wherein the polymerizedpolysiloxane unit is the reaction residue of its corresponding dihydroxycompound. In a specific embodiment, the polydiorganosiloxane blocks areprovided by repeating structural units of formula (14):

wherein R and D are as defined above. Each R⁵ in formula (14) isindependently a divalent C₂-C₈ aliphatic group. Each M in formula (14)may be the same or different, and may be a halogen, cyano, nitro, C₁-C₈alkylthio, C₁-C₈ alkyl, C₁-C₈ alkoxy, C₂-C₈ alkenyl, C₂-C₈ alkenyloxygroup, C₃-C₈ cycloalkyl, C₃-C₈ cycloalkoxy, C₆-C₁₀ aryl, C₆-C₁₀ aryloxy,C₇-C₁₂ arylalkyl, C₇-C₁₂ arylalkoxy, C₇-C₁₂ alkylaryl, or C₇-C₁₂alkylaryloxy, wherein each n is independently 0, 1, 2, 3, or 4.

Units of formula (14) may be derived from the corresponding dihydroxypolydiorganosiloxane (15):

wherein R, D, M, R⁵, and n are as described above. Such dihydroxypolysiloxanes can be made by effecting a platinum catalyzed additionbetween a siloxane hydride of formula (16):

wherein R and D are as previously defined, and an aliphaticallyunsaturated monohydric phenol.

In an embodiment, the polysiloxane-polycarbonate may comprisepolysiloxane units, and carbonate units derived from bisphenol-A, e.g.,the dihydroxy compound of formula (3) in which each of A¹ and A² isp-phenylene and Y¹ is isopropylidene. Polysiloxane-polycarbonates mayhave a weight average molecular weight of 2,000 to 100,000, specifically5,000 to 50,000 as measured by gel permeation chromatography using acrosslinked styrene-divinyl benzene column, at a sample concentration of1 milligram per milliliter, and as calibrated with polycarbonatestandards.

The polysiloxane-polycarbonate can have a melt volume flow rate,measured at 300° C. under a load of 1.2 kg, of 1 to 50 cubic centimetersper 10 minutes (cc/10 min), specifically 2 to 30 cc/10 min. Mixtures ofpolysiloxane-polycarbonates of different flow properties may be used toachieve the overall desired flow property. In an embodiment, exemplarypolysiloxane-polycarbonates are marketed under the trade name LEXAN® EXLpolycarbonates, available from SABIC Innovative Plastics.

The sheet further comprises a fluorescent dye. The term “fluorescent”refers to the emission of light by the dye, after absorbing lightradiation, at a defined wavelength (due to the Stokes shift). Bycomparison, a non-fluorescent dye does not absorb the energy and re-emitit at a defined wavelength, but as heat (i.e. a broad band ofradiation).

Dispersed within the sheet is a dye compound of Formula (I) or (II) asdescribed above, wherein each R and R′ is independently selected fromC₁-C₁₈ alkyl, substituted C₁-C₁₈ alkyl, C₁-C₁₈ alkoxy, substitutedC₁-C₁₈ alkoxy, and halogen; each m is independently an integer from 0 to5; and each k is independently an integer from 0 to 4. The term“dispersed” refers to the distribution of the dye within thethermoplastic polymer and is not intended to limit the means by whichthe dye is distributed within the polymer. In other words, the dye canbe “dispersed” by means including dispersing, dissolving, doping,emulsifying, etc.

The sheet of the solar collector has an edge emission output of about150 W/m² or greater when measured using a sheet of dimensions 60 mm×60mm×3.2 mm and exposed to a radiation intensity of about 1000 W/m²,including about 200 W/m² or greater, or 210 W/m² or greater. Whenmeasured, the sheet should have a smooth, high gloss surface; in otherwords, the surface should not be textured. The surface may have a 60degree gloss generally greater than about 95. The term “sheet” shouldnot be construed as limiting the method by which the thermoplastic partis manufactured. The sheet may be extruded, injection molded, orotherwise formed, as described further below. A sheet or plaque of thecorrect dimensions may be used to measure the edge emission output.

In particular embodiments, the sheet contains a dye compound of Formula(III), (IV), (V), or (VI).

If desired, additional fluorescent dyes may be included in the sheet.Exemplary dyes include the daylight fluorescent-type dyes that belong tothe dye families known as rhodamines, fluoresceins, coumarins,naphthalimides, benzoxanthenes, perylenes, pyrenes, acridines, or acombination comprising at least one of the foregoing. Examples includeluminescent dyes such as 7-amino-4-methylcoumarin;3-(2′-benzothiazolyl)-7-diethylaminocoumarin;2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole;2,5-bis-(4-biphenylyl)-oxazole; 2,2′-dimethyl-p-quaterphenyl;2,2-dimethyl-p-terphenyl; 3,5,3″″,5″″-tetra-t-butyl-p-quinquephenyl;2,5-diphenylfuran; 2,5-diphenyloxazole; 4,4′-diphenylstilbene;4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran;1,1′-diethyl-2,2′-carbocyanine iodide;3,3′-diethyl-4,4′,5,5′-dibenzothiatricarbocyanine iodide;7-dimethylamino-1-methyl-4-methoxy-8-azaquinolone-2;7-dimethylamino-4-methylquinolone-2;2-(4-(4-dimethylaminophenyl)-1,3-butadienyl)-3-ethylbenzothiazoliumperchlorate; 3-diethylamino-7-diethyliminophenoxazonium perchlorate;2-(1-naphthyl)-5-phenyloxazole; 2,2′-p-phenylen-bis(5-phenyloxazole);rhodamine 700; rhodamine 800; pyrene; chrysene; rubrene; coronene, orthe like; perylene dyes such as those based on imido derivatives ofperylene tetracarboxylic acid; or combinations comprising at least oneof the foregoing dyes. Suppliers of fluorescent colorants includeRadiant Color Company (Richmond, Calif.), Day-Glo Color Corp.(Cleveland, Ohio), Sun Chemical Co. (Cincinnati, Ohio). Sinloihi Co.Ltd. (Tokyo, Japan), Swada (London, England), Mikuni Color Works Ltd.(Himeji, Japan), Matsui International Co, Inc (Japan), Nippon KeikoColor Company (Japan). Specifically useful fluorescent dyes includethose available under the following tradenames: Diaresin® dyes fromMitsubishi Chemical (Japan); Lumogen® dyes from BASF (Germany),Irgalite® and Maxilon® dyes from Ciba Specialty Chemicals (Germany),Macrolex® dyes from Lanxess (Germany), and Hostasol® dyes from Clariant.Typical commercially available fluorescent dyes of the above typesinclude amino phthalate dyes such as Rhodamine BDC (C.I. 45,170),Rhodamine 6GDN extra (C.I. 45,160; Red 480), Rhodamine F5G (Red 482),Rhodamine FB (Red 540), and Rhodamine F3B (C.I. 45,175); naphthalimidederivatives such as Lumogen® F Blue 650; perylene derivatives such asLumogen® F Red 305; Lumogen® F Yellow 083; Lumogen® F Violet 570;Lumogen® F Green 850; Macrolex® Fluorescent Yellow 10GN (C.I. SolventYellow 160:1); Macrolex® Red G; Irgalite® Violet M, Maxilon® BrilliantFlavine 10GFF, Maxilon® Black FBL-01, Maxilon® Black RM-01, Maxilon®Blue 5G, Maxilon® Blue 5G-01, Maxilon® Blue GRL/Pearl, Maxilon® Blue GRLGranulated, Maxilon® Blue GRL E, Maxilon® Blue M-G, Maxilon® Blue TRLLiquid, Maxilon® Golden Yellow GL Pearls, Maxilon® Navy FRL-02, Maxilon®Red GRL-01 Pearl, Maxilon® Red GRL-E, Maxilon® Red GRL Pearls, Maxilon®Red M-4GL, Maxilon® Yellow M-3RL, and Maxilon® Yellow M-4GL; Hostasol®Red 5B (Vat Red 41), Hostasol® Red GG (Solvent Orange 63), and Hostasol®Yellow 3G (Solvent Yellow 98); Fluorescent yellow F6PN and Yellow Ytoner; Fluorescent Red 66; fluorescein; and 9-aminoacridine. Acombination comprising at least one of the foregoing fluorescent dyesmay be used. In an exemplary embodiment, fluorescent dyes useful hereininclude Lumogen® F Blue 650, Lumogen® Red 305, and Macrolex® FluorescentYellow 10GN. It will be understood that numerous fluorescent dyes areavailable commercially and are useful herein, and that therefore theforegoing list of fluorescent dyes should be considered exemplary, andnot limiting to the dyes disclosed hereinabove. The fluorescent dye isgenerally dispersed completely throughout the sheet.

The fluorescent dye may be covalently bonded to a polymeric backbone toprovide a polymer-supported fluorescent dye, and may also be referred toas dye conjugates. Such dye conjugates are useful to provide afluorescent dye that is predispersed, i.e., one that is distributedthroughout the polymer and which can provide a maximum fluorescence dueto the more uniform dispersion. Dyes which are not so dispersed mayaggregate or clump, and thereby decrease the effective loading of thedye based on the desired linear relationship between the fluorescentintensity and dye loading. Further, aromatic dyes, such as for examplepyrene-based dyes, can when held proximate to one another form dimericcomplexes (“excimers”) that can have a shifted absorbance and/orfluorescent emission wavelength and intensity relative to the parentnon-dimeric dye. Distributing the fluorescent dye along a polymerbackbone by covalent bonding can, in addition to the advantagesenumerated hereinabove, be used as a method to reduce or eliminateexcimer formation. Fluorescent dyes that are useful for preparing dyeconjugates include those having reactive functional groups capable offorming a covalent bond with a useful monomer or functional polymer orfunctional resin. Exemplary reactive groups provided by the fluorescentdye include phenolic hydroxy, aliphatic hydroxy, aromatic amine,aliphatic amine, thiols, carboxylic acid, and carboxylate esters. Itwill be understood that the foregoing list of reactive groups is meantto be exemplary, and should not be limited thereto.

Further functionalization of these functional fluorescent dyes, toprovide reactive derivatives, can further increase the reactiveusefulness of the fluorescent dye so functionalized. Reactivesubstituents can be formed by covalently reacting functional agents suchas, for example, reactive derivatives of (meth)acrylic acid such as(meth)acryloyl chloride; carbonyl dihalides such as phosgene;thiocarbonyl dihalides such as thiophosgene; maleic anhydride;chloroformates including alkyl, aryl, or aralkyl chloroformates,epichlorohydrin; or the like; to the above functional dyes to providesuitable reactive groups. In an exemplary embodiment, usefulfunctionalized fluorescent dyes include functional groups such as(meth)acrylates, (meth)acrylamides, N-hydroxysuccinimidyl (NHS) esters,isocyanates, isothiocyanates, maleimides, chloroformates, anhydrides,mixed anhydrides, epoxides, and the like. Polymeric backbone supportsfor such dyes can include linear polymers, crosslinked polymers,dendrimers, graft copolymers, block copolymers including two or moreblocks, end group modified polymers, hyperbranched copolymers,telechelic oligomers, or the like. Useful backbone polymers typicallyincludes poly(meth)acrylic homopolymers or copolymers includingpoly(meth)acrylates, poly(meth)acrylamides, and the like; poly(vinylaromatic) polymers and copolymers, including polystyrenes, copolymersthereof, and the like; polyvinyl polymers such as poly(vinyl acetate) orpoly(vinyl alcohol), copolymers thereof, and the like; poly(alkyleneoxide)s, copolymers thereof, and the like. In an embodiment, thefunctionalized fluorescent dye is attached to a polymer by reaction ofthe functional dye with a complementarily functionalized polymer. Inanother embodiment, the functionalized fluorescent dye having apolymerizable end group such as a (meth)acrylate or epoxide can becopolymerized with other monomers or reactive oligomers to provide apolymer-supported fluorescent dye. Other polymeric backbones that may beused as backbone support include polyesters, polycarbonates, polyimides,carbohydrate materials including substituted or unsubstituted cellulosicmaterials, polysaccharides, dextrins, aminosugars, and the like;proteins; or a combination comprising at least one of the foregoingpolymers. In an embodiment, the polymer-supported fluorescent dyesinclude fluorescent dyes incorporated into the polymeric backbone in anamount of 0.5 to 50 wt %, specifically 1 to 45 wt %, and morespecifically 5 to 40 wt %, based on the total weight of the fluorescentdye and polymer backbone.

A fluorescent brightener can also be included with the fluorescent dye.Fluorescent brighteners include fluorescent compounds which, whencombined with a dye having relatively low fluorescence, act to increasethe intensity of the fluorescent emissions from the dye combination. Inan embodiment, a fluorescent brightener is used in combination with ablue fluorescent dye. Exemplary fluorescent brighteners include thosemarketed under the tradename Uvitex® and available from Ciba SpecialtyChemicals, or DIPHYL® and BLANKOPHOR® available from Lanxess. In aspecific exemplary embodiment, a useful combination of a blue dye andfluorescent brightener includes Uvitex® OB, available from CibaSpecialty Chemicals, as fluorescent brightener. It will be understoodthat the foregoing fluorescent brightener is exemplary and should not beconsidered as limiting thereto. When used, a fluorescent brightener maybe included in an amount of from about 0.005 weight percent to about 25weight percent, specifically from about 0.01 weight percent to about 20weight percent, and more specifically from about 0.015 weight percent toabout 15 weight percent, based on the total weight of the sheet it isin.

The fluorescent dye of Formula (I) or (II) is generally used in amountsof from about 0.001 weight percent to about 1 weight percent,particularly from about 0.005 weight percent to about 0.1 weightpercent, and more particularly from about 0.02 weight percent to about0.05 weight percent, based on the total weight of the sheet.

In the luminescent solar collector, a sheet or panel as described aboveis operatively connected to a light energy converter, such as aphotovoltaic cell, or photocell. The photocell converts the light energyinto electrical energy. Several different types of photocells may beused. Suitable bulk technology photocells include amorphous siliconcells, multicrystalline silicon cells, and monocrystalline siliconcells. Suitable thin film technology photocells include cadmiumtelluride cells, copper indium selenide cells, gallium arsenide orindium selenide cells, and copper indium gallium selenide cells. Inspecific embodiments, the photocell is a multicrystalline siliconphotocell or a monocrystalline silicon photocell.

Generally, each type of photocell has a “sweet spot”, or a range ofwavelengths (light energy) which it converts most efficiently intoelectric energy. The photocell should be selected so that its sweet spotmatches, as much as possible, the light emitted by the sheet of the LSC.For example, the sweet spot of a multicrystalline silicon photocell or amonocrystalline silicon photocell is from about 700 nanometers to about1100 nanometers.

In addition to the components described hereinabove, the sheet mayfurther include various other additives ordinarily incorporated withthermoplastic compositions of this type, with the proviso that theadditives are selected so as not to adversely affect the desiredproperties of the thermoplastic composition. Mixtures of additives maybe used. Such additives may be mixed at a suitable time during themixing of the components for forming the thermoplastic composition.

Further non-limiting examples of additives that may be included in thesheet and/or the polymer layers include optical effects filler,antioxidant, heat stabilizer, light stabilizer, ultraviolet lightabsorber, plasticizer, mold release agent, lubricant, antistatic agent,flame retardant, anti-drip agent, gamma stabilizer, or a combinationcomprising at least one of the foregoing additives. Each of theseadditives can be present in amounts of from about 0.0001 to about 10weight percent, based on the total weight of the sheet and/or layer theadditive is in.

The sheet may be manufactured by methods generally available in the art.In particular, the dye compounds of Formula (I) or (II) can be easilyincorporated into polycarbonate or poly(methyl methacrylate) polymers togive a uniform dye dispersion. For example, in one embodiment, in onemanner of proceeding, powdered polycarbonate and fluorescent dye arefirst blended in a HENSCHEL-Mixer® high speed mixer. Other low shearprocesses including but not limited to hand mixing may also accomplishthis blending. The blend is then fed into the throat of an extruder viaa hopper. Alternatively, one or more of the components may beincorporated into the composition by feeding directly into the extruderat the throat and/or downstream through a sidestuffer. The fluorescentdyes of Formula (I) or (II) can be added either as a powder or as asolution in a suitable solvent. Generally, the dyes can be distributedwithin the polycarbonate using any means which accomplish the purpose,such as by dispersion. Additives may also be compounded into amasterbatch with a desired polymeric resin and fed into the extruder.The extruder is generally operated at a temperature higher than thatnecessary to cause the composition to flow. The extrudate is immediatelyquenched in a water batch and pelletized. The pellets, so prepared, whencutting the extrudate may be one-fourth inch long or less as desired.Such pellets may be used for subsequent molding, shaping, or forming.The sheet and/or polymer layers may be molded from the thermoplasticcomposition by a variety of means such as injection molding, extrusion,rotational molding, blow molding and thermoforming. In a specificembodiment, molding is done by injection molding.

The following examples are provided to illustrate the luminescent solarcollectors of the present disclosure. The examples are merelyillustrative and are not intended to limit devices made in accordancewith the disclosure to the materials, conditions, or process parametersset forth therein.

EXAMPLES Equipment

During compound synthesis, the compounds of Formula (I) were separatedusing a liquid chromatograph-mass spectrometer (LC-MS) system comprisinga liquid chromatograph and a Quattro® Ultima Pt mass spectrometer. AnXterra® C18 (50 mm×4.6 mm; 5 microns) column was used for separating thecomponents by liquid chromatography.

Proton NMR spectra were measured using a 300 MHz Bruker® NMRspectrometer. CDCl₃ was used as the recording solvent.

The absorption spectra and extinction coefficient were measured using adouble beam Perkins-Elmer® Lambda 900 UV-Vis-NIR spectrophotometer.Measurements were made in toluene or CHCl₃.

The emission spectra and quantum yield were measured with a Horiba JobinYvon Fluorolog®-3 fluorescence spectrophotometer, Model No: FL3-211.Measurements were made in toluene.

The decomposition temperature was measured by differential scanningcalorimetry (DSC) using a Q10 series machine from TA Instruments. Theincrease in temperature was 10° C./minute.

A solar simulator (PET SS200B simulator with a class B xenon lamp)illuminated each chip under AM1 illumination (air mass 1.5 spectralcurve) and a power of 1000 W/m² for an area of 200 mm×200 mm. Acalibrated Ocean Optics HD200 spectrophotometer (range 380 nm to 1100nm, resolution of 0.5 nm) with an optical fibre probe and attachedcollimating lens was used to determine the intensity of the edgeemission per area (W/m²). The spectrophotometer was calibrated over 300nm to 1050 nm using a bulb with a 3100K color temperature.

Example 1 Synthesis of Intermediate

1,6,7,12-tetrachloroperylene-3,4,9,10-tetradicarboxydianhydride (2grams, 3.8 mmol) and o-phenylenediamine (1.85 grams, 17.1 mmol) wereplaced into a 100 mL round bottom flask, and 30 mL propionic acid wasadded. The mixture was stirred at 140° C. for 6 hours, then cooled to80-90° C. and filtered hot using a glass sinter funnel. The intermediateproduct was then washed with 15 mL warm propionic acid followed by alarge excess of water. Next, the intermediate product was dried undersuction, then in an air oven at 80° C. for 10 hours. The yield of theintermediate product was 2.4 grams (˜62%). These steps were run multipletimes to obtain a quantity of intermediate product for use in thesubsequent Examples as described below.

Example 2 Synthesis of Formulas (III) and (IV)

The intermediate product synthesized in Example 1 (3 grams, 4.4 mmol),nonyl phenol (5.85 grams, 26.4 mmol) and potassium carbonate (3.65grams, 26.4 mmol) were added to 60 mL N-methylpyrrolidone. The reactionmixture was stirred at 150° C. for 24 hours, then cooled to roomtemperature. The reaction mixture was treated with chilled 10 mLconcentrated HCl in an ice bath until evolution of gas ceased. Theprecipitate obtained was filtered through a glass sinter funnel, washedrepeatedly with water, and then washed with 30 mL of methanol fivetimes. The yield was 2.1 grams (77% pure compound). It was then purifiedusing silica gel column chromatography using 10-30%dichloromethane-hexane mixture through gradual elution. The final yieldwas a 0.6 gram mixture of isomers Formula (III) and Formula (IV).

¹H-NMR for Formulas (III) and (IV) (CDCl₃): 8.56-8.42 (m, 4H),7.83-7.79(m, 2H), 7.50-7.43 (m, 4H), 7.33-7.20(m, 12H), 7.01-6.84(m,6H),1.85-1.56(m, 16H), 1.33-1.27(m, 20H), 0.91-0.43(m, 36H).

Example 3 Synthesis of Formula (V) and (VI)

The intermediate product synthesized in Example 1 (5 grams, 7.4 mmol),4-tert-octyl phenol (9.08 grams, 44 mmol) and potassium carbonate (6.07grams, 44 mmol) were taken in 150 mL N-methylpyrrolidone. The reactionmixture was stirred at 140° C. for 24 hours, then cooled to roomtemperature. The reaction mixture was treated with chilled 10 mLconcentrated HCl in an ice bath until evolution of gas ceased. Theprecipitate obtained was filtered through a glass sinter funnel, washedrepeatedly with water, and then washed with 30 mL of methanol fivetimes. It was then purified using silica gel column chromatography using10-30% dichloromethane-hexane mixture through gradual elution. The finalyield was a 2.0 gram mixture of isomers Formula (V) and Formula (VI).

¹H-NMR for Formulas (V) and (VI) (CDCl₃): 8.51-8.37 (m, 4H),7.79-7.78(m, 2H), 7.49-7.45 (m, 3H), 7.33-7.20(m, 13 H), 7.01-6.84(m,6H),1.84-1.76(m, 8H), 1.65-1.55 (m, 24H), 0.89-0.83(m, 36H).

Example 4 Synthesis of Formula (VII) and (VIII)

The intermediate product synthesized in Example 1 (5 grams, 7.4 mmol),4-tert-butyl phenol (6.66 grams, 44 mmol) and potassium carbonate (6.07grams, 44 mmol) were taken in 150 mL N-methylpyrrolidone. The reactionmixture was stirred at 140° C. for 24 hours, and then cooled to roomtemperature. The reaction mixture was treated with chilled 10 mLconcentrated HCl in an ice bath until evolution of gas ceased. Theprecipitate obtained was filtered through a glass sinter funnel, washedrepeatedly with water, and then washed with 30 mL of methanol fivetimes. It was then purified using silica gel column chromatography using10-30% dichloromethane-hexane mixture through gradual elution. The finalyield was a 1.70 gram mixture of isomers Formula (VII) and Formula(VIII).

¹H-NMR for Formulas (VII) and (VIII) (CDCl3): 8.57-8.15(m, 4H),7.86-7.47(m, 1H), 7.49-7.47(m, 3H), 7.3-7.26(m, 14H), 6.96-6.85(m, 6H),1.34(m, 36H tert-CH₃ group proton).

Comparison with Other Compounds

The compounds of Formulas (III) through (VIII) were compared to thefollowing comparative compounds: terrylene diimide, Violanthrone-79, andVat Green-1. These compounds are shown below:

The following Table 1 shows the photophysical properties of compounds ofFormulas (III) through (VIII) and the three comparative compounds. Thequantum yield was measured in chloroform:

TABLE 1 Extinction coefficient Decomposition λ_(abs) (L/cm ·λ_(emission) Temperature Quantum Compound (nm) mol) (nm) (° C.) DSCYield Formulas 630 63700 666 >378 1 (III) & (IV) Formulas 633 68039667 >350 0.96 (V) & (VI) Formulas 630 61200 666 >358 0.96 (VII) & (VIII)Terrylene 650 90000 680 357 0.54 diimide Violanthrone- 620 36246 720 3500.36 79 Vat Green-1 619 40974 720 >350 0.32

As seen here, the compounds of Formulas (III) through (VIII) have muchhigher quantum yields than the comparative compounds; they are allgreater than 95%. They absorb in the desired range (600-650 nm) and emitin the desired range (>650 nm).

Example 5

The three isomeric mixtures of Formulas (III) & (IV), Formulas (V) &(VI), and Formulas (VII) & (VIII) were then molded into plaques andtested for their edge emission output, as were two of the comparativecompounds, Violanthrone-79 and terrylene diimide.

The plaques were formed from a mixture of 1 kg polycarbonate andapproximately 100 milligrams dye. The polycarbonate was a bisphenol-Ahomopolycarbonate having a weight average molecular weight of 60,000versus polystyrene standards and a polydispersity of 2.1 to 2.3. Thepolycarbonate and dye were placed in a zip-lock polyethylene bag andshaken vigorously for about 3-4 minutes. The mixture was then extrudedto produce pellets. The extruded pellets were dried in an oven at 120°C. for about 6 hours, then molded using an LTM-Demag molding machine insquare plaques of 60 mm×60 mm, with 3.2 mm thickness.

The plaques were placed under a solar simulator (1000 W/m²) and the edgeemission output was measured. The results are shown in Table 2. The dyesof Formulas (III) & (IV), Formulas (V) & (VI), and Formulas (VII) &(VIII) all had a much higher edge emission than the comparativecompounds. The dyes of Formulas (VII) & (VIII), were the lowest of thethree isomeric mixtures.

TABLE 2 Compound Edge Emission (W/m²) Terrylene diimide 80Violanthrone-79 80 Formulas (III) & (IV) 221 Formulas (V) & (VI) 244Formulas (VII) & (VIII) 203

The dyes, luminescent solar collectors, and processes of the presentdisclosure have been described with reference to exemplary embodiments.Obviously, modifications and alterations will occur to others uponreading and understanding the preceding detailed description. It isintended that the exemplary embodiments be construed as including allsuch modifications and alterations insofar as they come within the scopeof the appended claims or the equivalents thereof.

1. A fluorescent dye selected from the group consisting of Formula (I)and Formula (II):

wherein each R and R′ is independently selected from C₈-C₁₈ alkyl,substituted C₈-C₁₈ alkyl, C₈-C₁₈ alkoxy, substituted C₈-C₁₈ alkoxy, andhalogen; m represents the number of R substitutents on each phenoxyring, wherein each m is independently an integer from 0 to 5; and krepresents the number of R′ substituents on each benzimidazole group,wherein each k is independently an integer from 0 to 4; and wherein eachphenoxy ring is substituted in only the para position with an R groupindependently selected from C₈-C₁₈ alkyl.
 2. The fluorescent dye ofclaim 1, wherein the four R groups in the para position are the same. 3.A fluorescent dye selected from the group consisting of Formula (I) andFormula (II):

wherein each R and R′ is independently selected from C₈-C₁₈ alkyl,substituted C₈-C₁₈ alkyl, C₈-C₁₈ alkoxy, substituted C₈-C₁₈ alkoxy, andhalogen; m represents the number of R substitutents on each phenoxyring, wherein each m is independently an integer from 0 to 5; and krepresents the number of R′ substituents on each benzimidazole group,wherein each k is independently an integer from 0 to 4; and wherein thefluorescent dye has a quantum yield of about 80% or greater.
 4. Thefluorescent dye of claim 3, wherein the fluorescent dye has a quantumyield of 90% or greater.
 5. The fluorescent dye of claim 3, wherein thefluorescent dye has a quantum yield of 95% or greater.
 6. A fluorescentdye selected from the group consisting of Formula (I) and Formula (II):

wherein each R and R′ is independently selected from C₈-C₁₈ alkyl,substituted C₈-C₁₈ alkyl, C₈-C₁₈ alkoxy, substituted C₈-C₁₈ alkoxy, andhalogen; m represents the number of R substitutents on each phenoxyring, wherein each m is independently an integer from 0 to 5; and krepresents the number of R′ substituents on each benzimidazole group,wherein each k is independently an integer from 0 to 4; and wherein thefluorescent dye has a maximum absorption wavelength of from about 600 nmto 650 nm and has a maximum emission wavelength of 650 nm or greater. 7.A fluorescent dye selected from the group consisting of Formulas (Ill),(IV), (V), and (VI):